Contrib module to examine client certificate

Following patch provides new contrib module pgsslinfo, which contains
several server-side functions, which allow to examine information about
SSL client certificate, used to connect to the server.

This information can be used for example, for logging user access.

Textual information from certificate distninguished name is converted
into current database charset, which allow non-latin characters in the
names to be readable.

Module was developed using latest stable version of OpenSSL (0.9.8b).
Probably, it should work with previous stable version of OpenSSL
(0.9.7something) which is still widely used, or even with outdated
version 0.9.6, but I haven't tested it.

Module requires access to PostgreSQL variable MyProcPort, which is not
declared DLLIMPORT in the appropriate header file (miscadmin.h).
So, this patch includes one-line patch to this header file, to allow
module compile and work under win32.